Loud-speaker



May 14,1940;

1. STEPHAN 2,201,059

LOUD-SPEAKER Filed Dec. 14, 19:57 2 Sheets-Sheet 1 May 14, 1940. TE H N 2,201,059

LOUD-SPEAKER Filed Dec. 14. 1937 2 Sheets-Sheet 2 Patented May 14, 1940 UNITE LOUD-SPEAKER Ingo L. Stephan, Beverly, N. .l., assignor to Philco Radio & Television Corporation, Philadelphia, Pa., a corporation of Delaware Application December 14, 1937, Serial No. 179,748

8 Claims.

This invention relates to new and useful improvements in voice coil supporting and centering spiders or diaphragms for sound reproducers of the electrodynamic type.

In loud-speakers of the electrodynamic type, the voice coil and the cylinder or former upon which it iswound are supported in the air gap of the electromagnet structure for free and unrestricted longitudinal or axial movement in said gap and constitute an actuator vfor the speaker cone or diaphragm which is connected thereto. The voice coil and its cylinder are usually supported and centered within this air gap by means of a diaphragm or spider of generally annular form through which the voice coil cylinder projects and to which it is secured by cement or glue, the outer peripheral portion of said centering spider being cemented or glued to a supporting portion afforded by the speaker cone frame structure. A speaker cone or diaphragm of generally annular irustoconical form is secured to this frame structure so that the voice coil cylinder projects through the central opening in the speaker cone and is secured to the edge portion thereof.

Ordinarily the voice coil supporting and centering spider or diaphragm is provided with a series of concentric corrugations intermediate its outer and inner peripheral edge portions, and these corrugations, as well as the inner and outer peripheral portions of the spider reside in substantially the same plane which, when mounted in the loud speaking device in the manner mentioned above, is disposed at right angles or perpendicular to the axis of the voice coil. In a similar manner the speaker cone is usually provided with a plurality of concentric corrugations adjacent its periphery.

Due to certain advantages, the majority of centering spiders and speaker cones manufactured or in use today are composed of some suitable fibrous material such as paper, Bakelite or cloth in one form or another. Each of these materials, however, have one common detriment in that they tend to expand radially when exposed or subjected to high humidity'and moisture. Accordingly, and although the concentric corrugations in the central portion of the spider and at the periphery of the speaker cone increase the axial freedom upon which their action depends, these corrugations do not constitute a re lief for such radial expansion and since both the spider and speaker cone are rigidly secured or mounted at their peripheries, expansion in each thereof must assume an inward direction, which in the case, of the speaker cone, tends to follow the conical slope thereof. This inward expansion of the speaker cone moves the centrally located voice coil cylinder in the direction of the air gap distorting the spider into a substantially conical shape in the same direction and causing the voice coil to be displaced wholly or partially below said gap with a resulting loss of efiiciency in the speaker and an increase of tone distortion due to the positioning of the voice coil out of the uniform and into a non-uniform part of the magnetic field supplied by the field magnet.

With these observations in mind, the principal object of the present invention is to provide a voice coil supporting and centering spider for electro-dynamic loud speakers which is constructed and arranged to counteract or oppose this tendency of the speaker cone and spider to settle or expand in the direction of the air gap as a result of the action of high humidity or moisture thereon, and conversely another object of the invention is to provide a voice coil supporting and centering spider of the character set forth wherein proper placement of the voice coil wholly within the air gap and the uniform magnetic field therein is at i all times assured and not affected by expansion of said spider.

These and other objects of the invention, as well as the features and details of its construction and arrangement are hereinafter fully set forth and shown in the accompanying drawings, in

which:

Figure 1 is a longitudinal section axially through a radio loud-speaker provided with a voice coil centering spider made according to this invention;

Figure 2 is a type plan. View of the voice coil centering spider;

Figure 3 is a view in section taken on line 3-3,Figure 2;

Figure 4. is a diagrammatic view showing the normal cross section shape of the speaker cone and the cross section shape thereof to which the conetends to assume when subjected to high humidity and moisture;

Figure 5 is a diagrammatic view illustrating the normal cross section shape of a spider made according to this invention and'the cross section shape to which it tends to assume when subjected to high humidity and moisture; and I Figure 6 is a diagrammatic view showing the normal cross section shapes of the present spider and speaker cone when secured to the voice coil cylinder and also shows the cross section shapes H to which said elements tend to assume when subjected to high humidity and moisture.

Referring now to the drawings, reference nu-- meral I designates the voice coil which as usual is wound upon a supporting cylinder or former 2 and disposed in the air gap provided between the core 3 and pole piece 4 of the field magnet. A frame or supporting structure 5 for the usual speaker diaphragm or cone 6 is secured to the magnet and its lower portion is formed to provide an annular support I.

The voice coil I and its cylinder 2 are accurately centered and supported within the airgap between the core 3 and pole piece 4 of the magnetic system by means of a generally annular diaphragm or spider 8 composed of suitable fibrous material such as paper, Bakelite, cloth or the like. The voice coil cylinder 2 projects through the central opening in the spider 8 and is secured by means of cement or glue to the inner edge 9 thereof while the outer peripheral edge portion I0 of said spider is secured by means of cement or glue to the annular support portion 1 of the speaker cone frame structure 5 previously described, the inner edge 9 and outer periphery I 0 of the spider preferably being serrated as described and claimed in the copending application of Joseph A. Briggs, filed Dec. 14, 1937, Serial No. 279,763.

As shown in Figure 2 of the drawings, the spider 8 is provided with a plurality of concentric corrugations I I therein intermediate the inner edge and outer peripheral portions 9 and I 0 thereof, and the particular feature of the present invention resides in the novel radial cross section shape or configuration of this concentrically corrugated portion of said spider which, as illustrated in Figure 3, is made concavo-convex in the direction of the speaker diaphragm or cone 6, or, in other words, in a direction away from the air gap between the pole piece I and core 3 of the magnetic system.

The centering and supporting spider 8 and speaker cone 6 are composed of suitable fibrous material such as paper, Bakelite, cloth or the like, and are, therefore, definitely affected by high humidity and moisture. Accordingly, as previously stated, with respect to the speaker cone, high humidity and moisture causes said speaker cone 6 to expand inwardly with the result that it is distorted, as illustrated in Figure 4 of the drawings, from its normal cross section shape shown in solid lines to substantially the cross section shape shown in dot and dash lines, This distortion or expansion of the cone 6 takes place in the direction of the air gap of the magnetic system and since the voice coil cylinder is connected to said core, the voice coil carried thereby is wholly or partially displaced from the air gap and the uniform magnetic field therein due to the fact that the supporting and centering.

spider 8 not only does not have suflicient rigidity or body to counteract such distortion of the cone 5 but itself expands with a resulting distortion also in the direction of the air gap of the magnetic system. I

I have found, however, that by making the radial cross section shape of the concentrically corrugated portion thereof substantially concavo-convex in a direction away from the air gap of the magnetic system, expansion and consequently distortion of the spider 8 caused by high humidity ormoisture takes place in a corresponding direction, as illustrated in Figure 5 or the drawings from the normal cross section shape shown in solid lines to substantially the cross section shape shown in dot and dash lines. Thus the resultant of this upward expansion or distortion of the spider 8 will operate to oppose or counteract distortion of the speaker cone 6 downwardly in the direction of the air gap as shown in Figure 4 with the result that when said spider 8 and speaker cone 6 are both secured in the usual relation to the voice coil cylinder, expansion or distortion of the cone 6, which would otherwise occur in the direction of the air gap, is neutralized so that the position of the cylinder and its voice coil axially of the pole piece wholly within the air gap and uniform magnetic field is permanently assured. Such neutralization of the downward expansion force of the cone 8, of course, cannot eliminate expansion of said cone 6 and spider 8 but the arrangement is such that expansion in these elements does not change the axial position of the cylinder and voice coil and operates as illustrated in Figure 6 of the drawings to expand said elements from their normal cross section shapes as shown in solid lines to substantially those shown in dot and dash lines.

The resultant force due to expansion of the spider 8 may be accurately controlled, as required to counteract expansion of the cone 5 in the direction of the air gap, by varying the radius or curvature of the concavo-convex concentrically corrugated portion of said spider, thus proper placement or position of the voice current coil I axially within the air gap may be attained and asured at all times without loss of efiiciency in operation, or without causing tone distortion, and unrestricted free movement of said voice coil axially in the air gap is retained unimpaired.

It will be obvious, of course, that the number of concentric corrugations employed as well as the particular radius or curvature of concavoconvex form of that portion of the spider will vary from time to time depending upon its size, the material of which composed, and the particular structure associated with it in a loudspeaking device, and while specific details of the invention have herein been illustrated and described, modifications and changes may be embodied or incorporated in the invention as desired within the scope of the annexed claims.

I claim:

1. In a sound reproducing device having a magnetic system including an air gap, a voice coil disposed in said air gap, a speaker cone operatively connected to said voice coil to be actuated thereby, and an annular supporting and centering element also operatively connectedto the voice coil and provided with a portion intermediate its inner and outer edges having an up Wardly arched substantially concavo 'convex radial cross section shape, said concave-convex portion of the element when expanded by the action of moisture being operative to introduce a force which tends to oppose the tendency of the cone to displace the voice coil from said air gap when similarly expanded.

2. In a sound reproducing device having a magnet system including an air gap, a voice coil disposed in said air gap, a speaker cone operatively connected to said voice coil to be actuated thereby, and an annular supporting and centering element also operatively connected to the voice coil and provided with a plurality of concentric corrugations intermediate its inner and outer edges, the corrugated portion of said element having a substantially concavo-convex radial cross section shape operative when expanded by the action of moisture to introduce a force which tends to oppose the tendency of the cone to displace the voice coil from the air gap when similarly expanded.

3. A supporting and centering device for the voice coil and connected speaker cone of sound reproducing devices comprising an annular element provided with a portion intermediate its inner and outer edges having an upwardly arched substantially concavo-convex cross section shape constructed and arranged to operate when expanded by the action of moisture to introduce a force which tends to oppose the tendency of the cone to displace the voice coil when similarly expanded.

4. A supporting and centering device for the voice coil and connected speaker cone of sound reproducing devices comprising an annular element provided with a plurality of concentric corrugations intermediate its inner and outer edges, the corrugated portion of said element having a substantially concavo-convex' radial cross section shape constructed and arranged to operate when expanded by the action of moisture to introduce a force which tends to oppose the tendency of the cone'to displace the .voice coil when similarly expanded.

5. A voice coil supporting and centering device of the character described comprising a thin flexible element of substantially annular form provided with a portion intermediate its inner and outer edges having an upwardly arched substantially concavo-convex radial cross section shape constructed and arranged so that expansion of said element caused by the action of moisture will take place in the direction of curvature of said concave-convex cross section shape.

6. A voice coil supporting and centering device of the character described comprising a thin flexible element of substantially annular form provided witha plurality of concentric corrugations intermediate itsinner and outer edge portions, the corrugated portion of said element having suficient radial length to permit of free axial movement thereof and having a substantially concavo-convex radial cross section contour constructed and arranged so that expansion of said element caused by the action of moisture will take place in the direction of curvature of said concavo-convex cross section shape.

'7. A voice coil supporting and centering device of the character described comprising a thin flexible element of substantially annular form provided with a portion intermediate its inner and outer edges havingan upwardly arched substantially concavo-convex 'radial cross section shape.

8. A voice coil supporting and centering device sufficient radial length to permit of substantially free axial movement thereof and having a substantially concavo-convex radial cross section contour.

INGO L. STEPHAN. 

